1. Field of the Invention
The present invention relates to an image recording method with which texture, such as the glossy feeling of the surface of a still subject or the fine texture of a fiber fabric, is represented on a recording medium such as recording paper. The present invention also relates to an ink jet printer that carries out the image recording method.
2. Description of the Related Art
Nowadays, it is possible to obtain a high-quality image by capturing a subject with a scanner or a camera. However, it is difficult to reproduce the texture of a subject having a substantially plane shape, such as the glossy feeling of the subject or the fine unevenness of the surface of the subject, with a captured image obtained by photographing the subject.
As a method of representing the texture of a subject, it is possible to cite processing based on a computer graphics (CG) technique. For instance, a specular reflectivity, a diffuse reflectivity, and the like that are information representing the texture of the subject are defined for three-dimensional data representing the subject on a computer, two-dimensional data is computed by performing rendering processing, and the data is displayed as a two-dimensional image.
When a person evaluates an object, he/she evaluates the object by picking it up and shaking it. That is, in general texture felt by a person, such as the glossy feeling of a subject, is obtained by changing the state of specular reflection of the subject through the changing of his/her viewpoint. Accordingly, in the case of the CG technique described above, it is required to repeatedly perform the rendering processing by dynamically changing specular reflection light through the slight changing of the direction in which the subject is illuminated. However, the processing amount of this rendering processing is large, so that there is a problem that an extremely long time is taken to perform the rendering processing.
Even if the processing speed of a computer is further improved in the future, it is still difficult to speedily create data about the shape of a subject and information about the texture thereof, which give a viewer real feeling, using the CG technique described above.
On the other hand, there is proposed a technique with which modeling of three-dimensional data having information about the texture of a subject is performed with a computer using images obtained by photographing the subject.
In JP 07-66436 B, JP 2001-108421 A, and the like, there is proposed a method with which three-dimensional data is obtained by taking a plurality of images from different viewpoints. With this method, however, specular reflection light and diffuse reflection light are not separated from each other, so that it is impossible to obtain sufficient information about the texture of a subject. Consequently, it is impossible to represent the texture of the subject as an image.
On the other hand, as a method of separating specular reflection light from diffuse reflection light for the sake of performing the three-dimensional modeling of a subject, there is proposed a method based on a dichroic reflection model (see xe2x80x9cExtraction of Specular Reflection Using Multiple Color and Range Imagesxe2x80x9d, Ohtsuki et al., Journal of the Institute of Electronics, Information and Communication Engineers, D-II, vol. J-80-D-II, No.6, pp. 1352-1359, June 1997).
With this method, however, it is required to perform statistical processing for estimating a color vector, which leads to a necessity that the surface of the subject has a moderate size and a uniform texture. Consequently, in the case where the subject has a construction where different materials and colors are combined in a fine manner, it is difficult to apply the method described above to this subject. Accordingly, it is difficult to represent the texture of the subject as an image.
On the other hand, in JP 08-39841 A, there is proposed a method with which a subject is photographed to obtain images having different illumination directions, there are obtained a signal under a state where reflection light is large and a signal under a state where reflection light is small, whereby a glossiness signal representing the glossiness of the subject is obtained from these two signals, a gloss being given by an image forming means using this signal. With this method, however, the glossiness signal is obtained by subtracting the signal under the state where the reflection light is small from the signal under the state where the reflection light is large, so that it is impossible to represent the texture of a fiber fabric or the like whose glossiness has a directional property due to fine unevenness of the subject. Further, an image forming means gives a gloss through reheating during thermal transfer, so that it is impossible to finely control the texture of a subject because of the widening of heat generated by the reheating. Accordingly, there is a problem that it is impossible to sufficiently represent a fiber fabric or the feeling of grain.
Accordingly, in order to solve the problems described above, an object of the present invention is to provide an image recording method which is capable of representing the texture, such as the glossy feeling of the surface of a subject or the fine texture of a fiber fabric, on a recording medium such as recording paper.
Another object of the present invention is to provide an ink jet printer that carries out the image recording method.
In order to attain the object described above, the present invention provides an image recording method of recording an image of a still subject on a recording medium using a diffuse reflection image signal of the image representing the still subject under a state where illumination light is diffuse-reflected and a glossiness signal representing glossiness of the still subject, comprising a diffuse reflection image forming step of forming a diffuse reflection image of the still subject on the recording medium based on the diffuse reflection image signal, and a gloss adjusting step of forming a gloss adjustment layer made of a transparent gloss adjustment material in each region in units of pixels of the diffuse reflection image formed on the recording medium based on signal values of the glossiness signal.
Here, in addition to an image obtained with a camera or a scanner, the image representing a still subject under a state where illumination light is diffuse-reflected includes a computer graphic image that has been created by performing computation processing based on three-dimensional data, such as a specular reflectivity and a diffuse reflectivity, and which represents the still subject under a state where illumination light is diffuse-reflected.
Preferably, the diffuse reflection image forming step and the gloss adjusting step are performed by allowing droplets to be ejected onto the recording medium.
And, the gloss adjustment material is one of a gloss suppression material and a gloss material.
Further, preferably, the gloss adjustment layer is formed in each region corresponding to one pixel of the diffuse reflection image formed on the recording medium in accordance with a formation pattern that has a formation distribution of the gloss adjustment layer that varies in accordance with the signal values of the glossiness signal. Here, preferably, the formation pattern has a two-dimensional formation distribution of the gloss adjustment layer within each region of each pixel.
Preferably, the glossiness signal contains a first and second glossiness signals, the gloss adjustment layer is formed in each region in units of pixels of the diffuse reflection image in accordance with the first glossiness signal and the second glossiness signal, and when the formation of the gloss adjustment layer is performed in accordance with the first glossiness signal or the second glossiness signal, an inclination is given to the thickness of the gloss adjustment layer, with a direction of the inclination being different between the first glossiness signal and the second glossiness signal.
Preferably, the glossiness signal further contains a third glossiness signals, the gloss adjustment layer is formed in each region in units of pixels of the diffuse reflection image in accordance with the first glossiness signal, the second glossiness signal and the third glossiness signal, when the formation of the gloss adjustment layer is performed in accordance with the third glossiness signal, a thickness of the gloss adjustment layer is made constant, and when the formation of the gloss adjustment layer is performed in accordance with one of the first glossiness signal and the second glossiness signal, an inclination is given to the thickness of the gloss adjustment layer, with a direction of the inclination being different between the first glossiness signal and the second glossiness signal.
Preferably, the glossiness signal is generated based on the diffuse reflection image signal and specular reflection image signal of the still subject obtained through specular reflection of illumination light, and the diffuse reflection image signal and the specular reflection image signal are respective image signals of a scan-captured image obtained by capturing the whole of the still subject while relatively moving a capturing position with respect to the still subject.
Here, preferably, the diffuse reflection image signal is an image signal of a captured image of the still subject obtained by capturing diffuse reflection light in which a reflection direction of reflection light from the still subject placed on a plane-shaped base and illuminated is in a relationship of diffuse reflection with respect to an incident direction of illumination light onto the still subject and a plane of the plane-shaped base, and the specular reflection image signal is an image signal of a captured image of the still subject obtained by capturing specular reflection light in which a reflection direction of reflection light from the still subject placed on the plane-shaped base and illuminated is in a relationship of substantially specular reflection with respect to an incident direction of illumination light onto the still subject and the plane of the plane-shaped base.
The diffuse reflection image signal may be an image signal obtained by illuminating the still subject from two different directions at the same time or an image signal composed of a first diffuse reflection image signal and a second diffuse reflection image signal obtained by illuminating the still subject from two different directions at different times.
Preferably, if the diffuse reflection image signal is an image signal obtained by illuminating the still subject from two different directions at the same time, the illumination light used to obtain the diffuse reflection image signal contains more diffused light components than the illumination light used to obtain the specular reflection image signal, and a signal value of the glossiness signal is obtained by subtracting a conversion value obtained by color-converting a signal value of the diffuse reflection image signal from a conversion value obtained by color-converting a signal value of the specular reflection image signal.
Meanwhile, if the diffuse reflection image signal is composed of a first diffuse reflection image signal and a second diffuse reflection image signal obtained by illuminating the still subject from two different directions at different times, the illumination light used to obtain the diffuse reflection image signal preferably contains more diffused light components than the illumination light used to obtain the specular reflection image signal.
Here, preferably, the glossiness signal contains a first, second and third glossiness signals generated based on the diffuse reflection image signal and the specular reflection image signal, a specular reflection image signal conversion value, a first diffuse reflection image signal conversion value, and a second diffuse reflection image signal conversion value are respectively obtained by color-converting a signal value of the specular reflection image signal, a signal value of the first diffuse reflection image signal and a signal value of the second diffuse reflection image signal, if a first condition that the specular reflection image signal conversion value is equal to or greater than an average value of the first diffuse reflection image signal conversion value and the second diffused reflection image signal conversion value is satisfied, a difference obtained by subtracting the average value from the specular reflection image signal conversion value is set as a signal value of a third glossiness signal and signal values of first and second glossiness signals are set at zero, if the first condition is not satisfied and a second condition that the first diffuse reflection image signal conversion value is equal to or greater than the second diffuse reflection image signal conversion value is satisfied, a difference obtained by subtracting the specular reflection image signal conversion value from the first diffuse reflection image signal conversion value is set as the signal value of the second glossiness signal and the signal values of the first and third glossiness signals are set at zero, and if neither of the first condition nor the second condition is satisfied, a difference obtained by subtracting the specular reflection image signal conversion value from the second diffuse reflection image signal conversion value is set as the signal value of the first glossiness signal and the signal values of the second and third glossiness signals are set at zero.
Further, preferably, the gloss adjustment layer is formed in each region in units of pixels of the diffuse reflection image in accordance with the first glossiness signal, the second glossiness signal and the third glossiness signal, when the formation of the gloss adjustment layer is performed in accordance with the third glossiness signal, a thickness of the gloss adjustment layer is made constant, and when the formation of the gloss adjustment layer is performed in accordance with one of the first glossiness signal and the second glossiness signal, an inclination is given to the thickness of the gloss adjustment layer, with a direction of the inclination being different between the first glossiness signal and the second glossiness signal.
In addition, the present invention provides an ink jet printer that records an image by ejecting droplets using a diffuse reflection image signal of an image representing a still subject under a state where illumination light is diffuse reflected and a glossiness signal representing glossiness of the still subject, comprising an ink jet head that forms a diffuse reflection image on a recording medium by ejecting ink droplets based on a supplied control signal and ejects transparent gloss adjustment liquid onto each region in units of pixels of the diffuse reflection image based on a supplied adjustment signal, and a control circuit that generates the control signal for ejecting the ink droplets based on the diffuse reflection signal, generates the adjustment signal for adjusting the ejection of the gloss adjustment liquid based on the glossiness signal, and supplies the control signal and the adjustment signal to the ink jet head.
Here, in addition to an image obtained with a camera or a scanner, the image representing a still subject under a state where illumination light is diffuse-reflected includes a computer graphic image that has been created by performing computation processing based on three-dimensional data, such as a specular reflectivity and a diffuse reflectivity, and which represents the texture of a subject or the like.